Combustion apparatus and hot water apparatus

ABSTRACT

A combustion apparatus includes a burner, a chamber, and a flame rod. The burner includes a burner port surface in which a plurality of burner ports are open. The chamber includes an attachment surface to which the burner is attached and supplies mixed gas to the plurality of burner ports. The flame rod is attached to a flange portion of a chamber located on an outer circumference side of the burner in plan view. The flame rod includes a core. The core extends diagonally to the attachment surface to pass through the chamber, and is bent toward the burner port surface.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a combustion apparatus and a hot water apparatus including the combustion apparatus.

Description of the Background Art

A combustion apparatus including a flame rod for sensing flames is disclosed in, for example, Japanese Patent Laying-Open No. 2018-071855. In this combustion apparatus, the flame rod is attached together with an ignition plug to a lateral wall of a case of a heat exchanger provided downstream of the combustion apparatus in a direction in which combustion gas circulates. The flame rod is bent, and the tip of the flame rod is disposed closer to a burner port surface than a portion of the flame rod, which is attached to the lateral wall of the case, is to the burner port surface.

SUMMARY OF THE INVENTION

In the combustion apparatus described in Japanese Patent Laying-Open No. 2018-071855, the flame rod is attached to the lateral wall of the case of the heat exchanger. The position on the lateral wall of the case of the heat exchanger at which the flame rod is attached is subject to constraints due to any other component of the heat exchanger, for example, a pipe through which hot water circulates. In the combustion apparatus, the flame rod is disposed relatively apart from the burner port surface of a burner due to such constrains.

An object of the present invention is to provide a combustion apparatus and a hot water apparatus that include a flame rod with high sensing performance.

A combustion apparatus according to the present invention includes a burner, a chamber, and a flame rod. The burner includes a burner port surface in which a plurality of burner ports are open. The chamber includes an attachment surface to which the burner is attached, and supplies mixed gas to the plurality of burner ports. The flame rod is attached to an outer circumferential portion of the chamber which is located on an outer circumference side of the burner in plan view. The flame rod includes a core. The core extends diagonally to the attachment surface to pass through the chamber, and is bent toward the burner port surface.

The flame rod can be disposed closer to the burner port surface in the combustion apparatus according to the present invention than in a conventional combustion apparatus. Consequently, the flame rod of the combustion apparatus according to the present invention has higher sensing performance than the flame rod of the conventional combustion apparatus.

In the combustion apparatus, the core includes a first portion having a tip end and disposed to extend along the burner port surface. The tip end is disposed opposite to the chamber with respect to the burner port surface and is disposed to overlap the burner in plan view. Consequently, compared with the flame rod of the conventional combustion apparatus, the flame rod of the above combustion apparatus has high performance of sensing a phenomenon in which flames are lifted due to a decreased oxygen concentration in the supplied air (hereinafter, hypoxia sensing performance) in order to prevent incomplete combustion.

In the combustion apparatus, the core includes a second portion inserted into the chamber, a third portion disposed between the first portion and the second portion, a first bent portion connecting the first portion and the third portion to each other, and a second bent portion connecting the second portion and the third portion to each other. This makes the position of the first portion resistant to constraints due to the angle of inclination of the core to the attachment surface compared with the case when the core includes a single bent portion between the first portion and the second portion. Thus, the first portion is disposed to extend along the burner port surface irrespective of the angle of inclination in the flame rod, easily enhancing hypoxia sensing performance.

The combustion apparatus further includes a burner flange disposed between the burner and the core such that at least part of the burner flange overlaps an outer edge portion of the burner in plan view. In the combustion apparatus, the burner flange is provided such that when the flame rod inserted into the chamber is disposed at a position different from a predetermined attachment position, the burner flange is disposed between the burner port surface and the core to prevent the core disposed at the different position from contacting the burner port surface. The burner flange can prevent damage to the burner port surface due to the contact of the core bent as described above with the burner port surface when the flame rod including the core is attached to the chamber.

In the combustion apparatus, the burner has a fibrous structure. The burner flange has a structure having a shape of a plate made of metal material, and the structure is more resistant to damage upon contact with the flame rod than the fibrous structure of the burner. Such a burner flange can prevent the flame rod from damaging the burner together with the burner flange when the flame rod contacts the burner flange.

In the combustion apparatus, the outer circumferential portion has a through-hole into which the flame rod is inserted, and a recess connected to an end on a burner side of the through-hole. The recess in a first direction extending toward an outer circumference of the burner has a width smaller than a width of the recess in a second direction orthogonal to the first direction. Such a recess can prevent the flame rod including the core bent as described above from interfering with the chamber when the flame rod is attached to the chamber.

In the combustion apparatus, the flame rod further includes an insulator covering part of the core. The combustion apparatus further includes a fixing portion that fixes the flame rod to the chamber. The fixing portion has an insertion hole into which the insulator is inserted. The insertion hole is provided to position the inserted flame rod with respect to the fixing portion. The fixing portion includes an engagement portion that engages with the chamber. The engagement portion is provided to position the fixing portion with respect to the chamber. Consequently, the combustion apparatus prevents the flame rod from being attached at a position different from a position predetermined with respect to the chamber.

A hot water apparatus according to the present invention includes the combustion apparatus and a heat exchange unit that heats hot water by combustion gas generated through combustion of mixed gas in the combustion apparatus. Consequently, a hot water apparatus can be provided that includes a combustion apparatus including a flame rod with high sensing performance.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a configuration of a hot water apparatus in an embodiment.

FIG. 2 is a perspective view showing an example configuration of a combustion apparatus and a sensible heat recovery heat exchanger shown in FIG. 1.

FIG. 3 is a partial sectional view as seen from an arrow in FIG. 2.

FIG. 4 is a partial plan view showing configurations of an attachment portion and a fixing portion of the combustion apparatus shown in FIG. 2.

FIG. 5 is a partial perspective view showing the configurations of the attachment portion and the fixing portion of the combustion apparatus shown in FIG. 2.

FIG. 6 is a partial sectional view showing a configuration of a recess of the combustion apparatus shown in FIG. 2.

FIG. 7 is a partial sectional view showing how a flame rod of the combustion apparatus shown in FIG. 2 is attached to a chamber.

FIG. 8 shows a cross section of the combustion apparatus shown in FIG. 7 taken in a direction of a hole axis of a through-hole and also in a direction perpendicular to the sheet of paper of FIG. 7, which is a partial sectional view of a burner flange side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described below with reference to the drawings. In the following description, “in plan view” refers to a point of view from a direction orthogonal to an attachment surface 31 i of a chamber 31 to which a burner 30 is attached. A configuration of a hot water apparatus in an embodiment of the present invention will now be described with reference to FIG. 1.

As shown in FIG. 1, a hot water apparatus 100 of the present embodiment mainly includes a sensible heat recovery heat exchanger (primary heat exchanger) 10, a latent heat recovery heat exchanger (secondary heat exchanger) 20, burner 30, chamber 31, a fan (fan assembly) 32, a duct 33, a venturi 34, an orifice 35, a gas valve 36, a pipe 40, a bypass pipe 41, and a housing 50. All the above components except for housing 50 are disposed inside housing 50.

Gas valve 36, orifice 35, and venturi 34 are connected to a pipe in the stated order. Fuel gas can be supplied to this pipe from the outside of housing 50. The fuel gas supplied to this pipe flows through gas valve 36 and orifice 35 into venturi 34.

Gas valve 36 serves to switch supply and stop of the fuel gas and set the gas pressure at an inlet of venturi 34 to be equal to an air pressure. Venturi 34 serves to increase the velocity of flow of air to increase a negative pressure of a fuel gas introducing portion, thereby facilitating an inflow of the fuel gas. Venturi 34 is configured to take in air from the outside of housing 50. Venturi 34 is configured to mix the air taken in from the outside of housing 50 and the fuel gas supplied through the pipe.

Venturi 34 is connected to fan 32 through a pipe. Through this pipe, the mixed gas mixed in venturi 34 is fed to fan 32. Fan 32 serves to supply the mixed gas to burner 30. Fan 32 mainly includes a fan case, an impeller disposed in the fan case, and a driving source (e.g., motor) for rotating the impeller.

Fan 32 is connected to chamber 31, and chamber 31 is connected to burner 30. The mixed gas supplied from fan 32 is fed to burner 30 through chamber 31.

Burner 30 serves to burn mixed gas to generate combustion gas serving as gas for heating. Burner 30 is a device of inverse combustion type which supplies combustion gas downward. The mixed gas blown out of burner 30 is ignited by an ignition plug 14 to turn into combustion gas. Ignition plug 14 is disposed downstream of burner 30 in the direction in which mixed gas circulates and is attached to, for example, sensible heat recovery heat exchanger 10. Flames produced in burner 30 through combustion of the mixed gas is sensed by a flame rod 15. Flame rod 15 is disposed downstream of burner 30 in the direction in which mixed gas flows and is attached to chamber 31. Flame rod 15 will be described below in detail.

Burner 30, sensible heat recovery heat exchanger 10, and latent heat recovery heat exchanger 20 are connected to allow combustion gas to flow through sensible heat recovery heat exchanger 10 and latent heat recovery heat exchanger 20 in order. Specifically, sensible heat recovery heat exchanger 10 is attached below burner 30, and latent heat recovery heat exchanger 20 is attached below sensible heat recovery heat exchanger 10.

Latent heat recovery heat exchanger 20 is connected with duct 33, and duct 33 runs to the outside of housing 50. Consequently, the combustion gas that has flowed through latent heat recovery heat exchanger 20 is discharged to the outside of housing 50 through duct 33.

Each of sensible heat recovery heat exchanger 10 and latent heat recovery heat exchanger 20 serves to heat hot water through heat exchange between the combustion gas supplied from burner 30 and hot water.

Sensible heat recovery heat exchanger 10 serves to recover a sensible heat of the combustion gas generated by burner 30. Sensible heat recovery heat exchanger 10 mainly includes a case 11 and a heat absorption pipe 13 (FIGS. 3 and 4). Latent heat recovery heat exchanger 20 serves to recover a latent heat of the combustion gas. Latent heat recovery heat exchanger 20 may be, for example, a plate type heat exchanger.

For example, when the temperature of the hot water introduced to sensible heat recovery heat exchanger 10 is low, or when an amount of heating by burner 30 is small, water vapors of the combustion gas condenses in sensible heat recovery heat exchanger 10, generating condensed water (drainage water). Drainage water is generated also in latent heat recovery heat exchanger 20. Such drainage water flows through part of duct 33 to be discharged to the outside of housing 50.

Heat absorption pipe 13 of sensible heat recovery heat exchanger 10 and a heat transfer portion of latent heat recovery heat exchanger 20 are connected to each other by pipe 40. A portion of pipe 40, which is on the water entry side with respect to latent heat recovery heat exchanger 20, and a portion of pipe 40, which is on the hot water exit side with respect to sensible heat recovery heat exchanger 10, are bypassed by bypass pipe 41.

Bypass pipe 41 is connected with a bypass servo 42. Bypass servo 42 is configured to control a flow rate of water flowing through bypass pipe 41.

The water supplied to hot water apparatus 100 turns into hot water through heat exchange with the combustion gas in sensible heat recovery heat exchanger 10 and latent heat recovery heat exchanger 20. This allows hot water apparatus 100 to supply hot water.

A configuration of a combustion apparatus 200 for use in hot water apparatus 100 described above will now be described with reference to FIGS. 1 to 8. Although FIGS. 7 and 8 are partial sectional views showing a state in which flame rod 15 is being attached to a flange portion 31 a, flame rod 15 is not shown in cross section in FIGS. 7 and 8. FIG. 7 shows a cross section which passes through the hole axis of a through-hole 31 c and is perpendicular to the direction of extension of flange portion 31 a. FIG. 8 shows a cross section of a burner flange 37 side, which is seen from a cross section passing through the hole axis of through-hole 31 c and perpendicular to the sheet of paper of FIG. 7.

As shown in FIGS. 1 to 3, combustion apparatus 200 includes burner 30, chamber 31, burner flange 37, ignition plug 14, flame rod 15, a pressing member 16 and a fixing member 17 which serve as a fixing portion, and a sealing member 18. As shown in FIG. 3, burner 30 includes a burner port surface 30 b in which a plurality of burner ports 30 a are open. Burner 30 burns the mixed gas which has passed through burner ports 30 a and been supplied to burner port surface 30 b, thereby generating flames. Burner port surface 30 b is, for example, a curved surface with the center of curvature which is disposed above burner 30. Burner ports 30 a are disposed, for example, inside of the outer edge portion of burner 30 in plan view and is not provided on the outer edge portion of burner 30. The hole axes of burner ports 30 a are provided to be orthogonal to burner port surface 30 b. Burner 30 is connected to an exhaust vent of chamber 31. Burner 30 is, for example, disposed to overlap the entire exhaust vent 31 h of chamber 31 in plan view. Burner 30 has a fibrous structure. Herein, the fibrous structure refers to a structure formed of woven fibers.

As shown in FIG. 3, chamber 31 supplies the mixed gas supplied from fan 32 to burner ports 30 a of burner 30. Chamber 31 has an inlet port connected to fan 32 and an exhaust vent 31 h connected to burner 30. Chamber 31 includes a flange portion 31 a (outer circumferential portion) disposed outside of burner 30 and exhaust vent 31 h in plan view. Flange portion 31 a is disposed annularly so as to surround the outer circumferences of burner 30 and exhaust vent 31 h in plan view.

As shown in FIGS. 2 to 4, flange portion 31 a includes an outer circumferential region connected to the upper end of sensible heat recovery heat exchanger 10 with sealing member 38 therebetween, an inner circumferential region connected to burner flange 37 with sealing member 39 therebetween, and an attachment portion 31 b which is disposed between the outer circumferential region and the inner circumferential region and to which flame rod 15 is attached. The lower surface of the inner circumferential region of flange portion 31 a is attachment surface 31 i to which burner 30 is attached with burner flange 37 therebetween.

As shown in FIG. 3, attachment portion 31 b has a through-hole 31 c passing through the upper surface and the lower surface of attachment portion 31 b. The hole axis of through-hole 31 c is inclined to attachment surface 31 i. The upper surface of attachment portion 31 b is an inclined surface 31 d inclined to the upper surface of the portion of flange portion 31 a other than attachment portion 31 b. Inclined surface 31 d is inclined to extend upward as closer to the inside in plan view. The upper end of through-hole 31 c is open in inclined surface 31 d.

As shown in FIGS. 4 and 5, attachment portion 31 b further has a first lateral surface 31 f and a second lateral surface 31 g, which extend in the direction crossing inclined surface 31 d and are disposed with inclined surface 31 d therebetween. First lateral surface 31 f and second lateral surface 31 g are inclined to the upper surface of the portion of flange portion 31 a other than attachment portion 31 b. A distance W1 between through-hole 31 c and first lateral surface 31 f is smaller than a distance W2 between through-hole 31 c and second lateral surface 31 g.

The lower surface of attachment portion 31 b faces the interior of case 11, and is configured as the inner circumferential surface of a recess 31 e recessed with respect to the lower surface of the portion of flange portion 31 a other than attachment portion 31 b. Recess 31 e will be described below in detail.

As shown in FIG. 3, the hole axis of through-hole 31 c is inclined to the upper surface of flange portion 31 a. One end of through-hole 31 c faces the outside of chamber 31 and case 11. The other end of through-hole 31 c faces the interior of case 11 of sensible heat recovery heat exchanger 10. The other end of through-hole 31 c is disposed inside of and below the one end of through-hole 31 c in plan view. The opening of through-hole 31 c can have any appropriate shape, which is a circular shape, for example.

Burner flange 37 is disposed annularly so as to surround burner ports 30 a in plan view. As shown in FIG. 3, burner flange 37 includes an inner circumferential portion 37 a, which is disposed to overlap the outer edge portion of burner 30 in plan view, and an outer circumferential portion 37 b, which is disposed to surround the outer edge portion of burner 30 in plan view. Inner circumferential portion 37 a of burner flange 37 is disposed on the tip end 15T side of flame rod 15 with respect to burner port surface 30 b, that is, on the sensible heat recovery heat exchanger 10 side. Outer circumferential portion 37 b of burner flange 37 is attached to flange portion 31 a. Consequently, burner flange 37 supports burner 30 with respect to chamber 31.

Burner flange 37 has a structure having the shape of a plate made of metal material, which is more resistant to damage upon contact with the flame rod than burner 30 having a fibrous structure.

As shown in FIG. 2, ignition plug 14 includes a pair of ignition plug electrodes. Ignition plug 14 generates ignition sparks between the pair of ignition plug electrodes, thereby producing flames in the mixed gas issued from burner 30.

As shown in FIGS. 2 and 3, ignition plug 14 is attached to a wall surface of case 11. Ignition plug 14 is attached to case 11 while passing through case 11. Ignition plug 14 is disposed between heat absorption pipe 13 of heat absorption pipes 13 disposed adjacent to case 11, which is closest to burner 30, that is, heat absorption pipe 13 located uppermost, and heat absorption pipe 13 disposed directly below the above-mentioned heat absorption pipe 13, that is, heat absorption pipe 13 located second from the top.

Ignition plug 14 includes a core, which is made of conductive material, and an insulator, which is made of electrical insulating material and covers part of the core. The core of ignition plug 14 has a tip end 14T located inside case 11. The core of ignition plug 14 is bent at one location inside case 11. The core of ignition plug 14 includes a portion extending, for example, horizontally, a portion extending toward burner 30 with respect to the above-mentioned portion, and a bent portion connecting the above-mentioned two portions. The portion of the core of ignition plug 14 which extends horizontally is attached to case 11 with the insulator therebetween. The portion of the core of ignition plug 14 which extends toward burner 30 has tip end 14T.

Flame rod 15 applies an ac voltage across the flames generated in burner 30 and uses at least any one of the conductivity and rectification owing to ionization of the combustion gas in the flames to sense a dc current flowing from flame rod 15 to the flames, thereby sensing flames.

As shown in FIGS. 2 and 3, flame rod 15 is attached to flange portion 31 a of chamber 31. Flame rod 15 has one end 15S and tip end 15T. One end 15S is disposed on the chamber 31 side with respect to burner port surface 30 b and is disposed outside of burner 30 in plan view. Tip end 15T is disposed opposite to chamber 31 with respect to burner port surface 30 b and is disposed to overlap burner 30 in plan view. Tip end 15T is spaced from burner port surface 30 b in the direction perpendicular to burner port surface 30 b. Preferably, combustion apparatus 200 further includes a flame rod 19 attached to case 11, in addition to flame rod 15. Two flame rods 15 and 19, which have different distances from burner port surface 30 b, enhance hypoxia sensing performance more than when any one of these flame rods is used. It suffices that flame rod 19 has a configuration similar to that of the flame rod of the conventional combustion apparatus.

Flame rod 15 includes a core 15 a made of conductive material and having one end 15S and tip end 15T, and an insulator 15 b made of electrical insulating material and covering part of core 15 a. Core 15 a of flame rod 15 is bent at at least two locations within case 11. Points at which core 15 a of flame rod 15 is bent are more than the points at which the core of ignition plug 14 is bent.

Core 15 a includes a first portion 15 aa having tip end 15T, a second portion 15 ab having one end 15S, a third portion 15 ac, a first bent portion 15 ad, and a second bent portion 15 ae. Part of second portion 15 ab of core 15 a is covered with insulator 15 b. First portion 15 aa, third portion 15 ac, first bent portion 15 ad, and second bent portion 15 ae of core 15 a are not covered with insulator 15 b and are exposed to the interior of case 11.

First portion 15 aa is disposed to extend along burner port surface 30 b. In other words, the distance between first portion 15 aa and burner port surface 30 b is provided to be approximately constant.

A part of second portion 15 ab is disposed outside of chamber 31 and case 11. Another part of second portion 15 ab is disposed in case 11. The remaining part of second portion 15 ab is inserted into through-hole 31 c of flange portion 31 a.

Third portion 15 ac is disposed between first portion 15 aa and second portion 15 ab. First bent portion 15 ad connects first portion 15 aa and third portion 15 ac to each other.

First bent portion 15 ad is disposed not to overlap burner port surface 30 b but to overlap burner flange 37 as viewed from the direction perpendicular to burner port surface 30 b. From a different perspective, first bent portion 15 ad is disposed outside of a space defined between a surface of projection, which is obtained by projecting burner port surface 30 b in the direction perpendicular to burner port surface 30 b, and burner port surface 30 b. A first angle formed between first portion 15 aa and third portion 15 ac in first bent portion 15 ad is, for example, an obtuse angle.

Second bent portion 15 ae connects second portion 15 ab and third portion 15 ac to each other. A second angle formed between second portion 15 ab and third portion 15 ac in second bent portion 15 ae is, for example, an obtuse angle. For example, the first angle is larger than the second angle. The first angle is larger than, for example, the angle of bend of the core of ignition plug 14. The second angle is smaller than, for example, the angle of bend of the core of ignition plug 14.

As shown in FIG. 3, insulator 15 b includes a main body 15 ba and a projection 15 bb. Main body 15 ba holds second portion 15 ab of core 15 a. Main body 15 ba has one end, which is located on the one end 15S side of core 15 a and is disposed outside of chamber 31 and case 11, and the other end, which is located on the tip end 15T side of core 15 a and is disposed inside of case 11. Projection 15 bb projects outward from the outer circumferential surface of the portion located between the one end and the other end of main body 15 ba. The portion of main body 15 ba, which is located on the one end side with respect to projection 15 bb, and projection 15 bb are disposed outside of chamber 31 and case 11. Of the portion of main body 15 ba which is located on the other end side with respect to projection 15 bb, a part is inserted into through-hole 31 c, and the remaining part is disposed inside of case 11. The portion of main body 15 ba which is located on the other end side with respect to projection 15 bb is rotatable about core 15 a in through-hole 31 c. In other words, the portion of main body 15 ba which is located on the other end side with respect to projection 15 bb is provided not to interfere with through-hole 31 c when this portion rotates about core 15 a in through-hole 31 c. The planar shape of the portion of main body 15 ba which is located on the other end side with respect to projection 15 bb is symmetrical with respect to the center of core 15 a, which is a circular shape, for example.

As shown in FIG. 4, the planar shape of the portion of main body 15 ba which is located on the one end side with respect to projection 15 bb, that is, the portion which is not inserted into through-hole 31 c is asymmetrical with respect to the center of core 15 a.

The fixing portion is provided to regulate the movement of flame rod 15 with respect to flange portion 31 a. The fixing portion is provided to regulate the movement of flame rod 15 in the direction of the hole axis of through-hole 31 c with respect to flange portion 31 a from a state in which flame rod 15 is disposed at a position predetermined with respect to flange portion 31, which is a first position (hereinafter, first state). Further, the fixing portion is provided to regulate the rotation of flame rod 15 with respect to flange portion 31 a in the circumferential direction about the hole axis of through-hole 31 c from the first state. The predetermined position is the position of flame rod 15 shown in FIG. 4, at which first portion 15 aa is disposed along burner port surface 30 b and flame rod 15 can achieve the intended sensing performance (improvements in flame sensing performance and hypoxia sensing performance).

The fixing portion includes pressing member 16 and fixing member 17. Pressing member 16 presses projection 15 bb and sealing member 18 from the side opposite to attachment portion 31 b in the first state.

Pressing member 16 includes a facing portion 16 a, a pair of contact portions 16 b, and at least one protrusion 16 d (engagement portion). Facing portion 16 a faces inclined surface 31 d and is provided to sandwich projection 15 bb and sealing member 18 between inclined surface 31 d and facing portion 16 a in the first state. Facing portion 16 a further has a second through-hole 16 c into which the portion of main body 15 ba of insulator 15 b which is located on the one end side with respect to projection 15 bb is inserted. The planar shape of second through-hole 16 c is asymmetrical with respect to the center of second through-hole 16 c. Facing portion 16 a further has a plurality of third insertion holes into which fixing member 17 is inserted. The third insertion holes are provided to sandwich second through-hole 16 c therebetween.

Each contact portion 16 b bends with respect to facing portion 16 a. Each contact portion 16 b is provided to contact inclined surface 31 d in the first state. Each of contact portions 16 b is connected to, for example, a corresponding one of the opposite ends of facing portion 16 a which are opposed to each other with the second through-hole therebetween. When the planar shape of facing portion 16 a has a longitudinal direction and a transverse direction, the pair of contact portions 16 b are preferably connected to the opposite ends in the transverse direction of facing portion 16 a.

The pair of contact portions 16 b have an equal width in the direction of the hole axis of second through-hole 16 c. The width of each contact portion 16 b in the direction of the hole axis of second through-hole 16 c is smaller than the sum of the width of projection 15 bb in the direction of extension of core 15 a and the thickness of sealing member 18 which is not pressed. The width of each contact portion 16 b in the direction of the hole axis of second through-hole 16 c is designed as a value obtained by subtracting a predetermined rate of squeeze of sealing member 18 from the sum. This can reduce variations in the rate of squeeze of sealing member 18 located on one side with respect to second through-hole 16 c and the rate of squeeze of sealing member 18 on the other side, for example, if there are variations in the torque acting on sealing member 18 in fastening of a machine screw when fixing member 17 is the machine screw.

As shown in FIGS. 4 and 5, protrusion 16 d is connected to facing portion 16 a. Protrusion 16 d projects toward the side opposite to facing portion 16 a with respect to contact portion 16 b. When the planar shape of facing portion 16 a has a longitudinal direction and a transverse direction, protrusion 16 d is connected only to one end in the longitudinal direction of facing portion 16 a.

As shown in FIG. 4, the distance between the surface of protrusion 16 d which is directed toward second through-hole 16 c and second through-hole 16 c is equal to distance W1 between second through-hole 16 c and first lateral surface 31 f. Consequently, in the state in which flame rod 15 is located at the first position, protrusion 16 d contacts first lateral surface 31 f and facing portion 16 a is held parallel to inclined surface 31 d, so that flame rod 15 is appropriately attached to flange portion 31 a. Contrastingly, in the state in which protrusion 16 d rotates 180 degrees about the center of second through-hole 16 c with respect to the first position, protrusion 16 d contacts inclined surface 31 d and facing portion 16 a is inclined with respect to inclined surface 31 d, so that flame rod 15 interferes with through-hole 31 c and cannot be inserted into through-hole 31 c.

Fixing member 17 may be, for example, a screwing member such as machine screw, screw, or bolt, or may be a pin. Sealing member 18 is, for example, rubber packing. Sealing member 18, which is pressed as described above, is pressed in its thickness direction and seals through-hole 31 c.

As shown in FIGS. 7 and 8, recess 31 e is provided not to interfere with flame rod 15 rotated with respect to flange portion 31 a when flame rod 15 is attached to flange portion 31 a.

As shown in FIGS. 3, 7, and 8, recess 31 e has a bottom surface facing downward and a lateral surface surrounding the bottom surface. The bottom surface of recess 31 e is recessed with respect to the lower surface in the outer circumferential region of flange portion 31 a and the lower surface in the inner circumferential region of flange portion 31 a. The lateral surface of recess 31 e connects the bottom surface of recess 31 e to the lower surface in the outer circumferential region of flange portion 31 a and the lower surface in the inner circumferential region of flange portion 31 a. Through-hole 31 c is open in the bottom surface of recess 31 e and in the lateral surface connecting the bottom surface of recess 31 e and the lower surface of flange portion 31 a in the outer circumferential region to each other. As shown in FIG. 8, through-hole 31 c is disposed, for example, while being closer to one side with respect to the center of recess 31 e in the direction of extension of flange portion 31 a.

As shown in FIG. 6, in plan view, a width W3 of recess 31 e in the direction of extension of flange portion 31 a is larger than a width W4 of recess 31 e in the direction perpendicular to the direction of extension of flange portion 31 a. From a different perspective, width W4 of the recess in the first direction extending from the center of burner 30 toward the outer circumference of burner 30 in plan view is smaller than width W3 of the recess in the second direction orthogonal to the first direction in plan view.

For example, flame rod 15 is attached to flange portion 31 a as follows.

First, flame rod 15 and pressing member 16 aligned to each other are prepared. Specifically, as insulator 15 b is inserted into second through-hole 16 c of pressing member 16, flame rod 15 is positioned with respect to pressing member 16. Also, sealing member 18 is disposed to surround second through-hole 16 c.

Subsequently, the portion of core 15 a of flame rod 15 which is located on the tip end 15T side with respect to insulator 15 b is inserted into through-hole 31 c. Subsequently, insulator 15 b is inserted into through-hole 31 c. At this time, arrangement is made such that the central axis of insulator 15 b extends along the hole axis of through-hole 31 c, as shown in FIG. 7. Further, arrangement is made such that the portions of core 15 a of flame rod 15 overlap the hole axis of through-hole 31 c as viewed from the direction of extension of flange portion 31 a. At this time, as recess 31 e is provided in flange portion 31 a, the interference between first portion 15 aa and flange portion 31 a is prevented. Part of first portion 15 aa is disposed in recess 31 e, and the remaining part of first portion 15 aa which includes tip end 15T is disposed outside of recess 31 e and inside of case 11. At this time, pressing member 16 is positioned so as not to engage with attachment portion 31 b.

Subsequently, when flame rod 15 moves along the hole axis of through-hole 31 c, the portion of core 15 a which is located on the tip end 15T side with respect to insulator 15 b also moves along the hole axis. After projection 15 bb contacts inclined surface 31 d, flame rod 15 is rotated relative to flange portion 31 a. Flame rod 15 is rotated relative to flange portion 31 a by, for example, 90 degrees. In this manner, pressing member 16 is positioned so as to be fixed to attachment portion 31 b. Further, when pressing member 16 is positioned so as to be fixed to attachment portion 31 b, flame rod 15 positioned with respect to pressing member 16 is disposed at a position predetermined with respect to flange portion 31 a as shown in FIG. 3. At this time, facing portion 16 a sandwiches projection 15 bb and sealing member 18 between inclined surface 31 d and facing portion 16 a, contact portion 16 b contacts inclined surface 31 d, and protrusion 16 d contacts attachment portion 31 b and first lateral surface 31 f. Subsequently, fixing member 17 is inserted into the third insertion hole of pressing member 16 disposed at the above position to be fixed to flange portion 31 a. Consequently, flame rod 15 is fixed to flange portion 31 a.

Before projection 15 bb contacts inclined surface 31 d, when flame rod 15 is rotated relative to flange portion 31 a, for example, part of core 15 a, such as first portion 15 aa and first bent portion 15 ad, may contact burner flange 37. Since burner flange 37 is provided so as not be damaged even when being pressed by core 15 a, the contact between core 15 a of flame rod 15 and burner 30 is prevented by burner flange 37.

The functions and effects of the present embodiment will now be described in comparison with the conventional combustion apparatus.

As described above, the flame rod is attached to the lateral wall of the case of the heat exchanger in the conventional combustion apparatus. The position on the lateral wall of the case of the heat exchanger at which the flame rod is attached is subject to constraints due to another component of the heat exchanger, such as a pipe through which hot water circulates. Due to such constraints, the flame rod is disposed relatively apart from the burner port surface of the burner in the above hot water apparatus.

Contrastingly, in the present embodiment, flame rod 15 is attached to flange portion 31 a of chamber 31 which is located closer to burner 30 than case 11 is to burner 30. Further, in core 15 a of flame rod 15, second portion 15 ab inserted into through-hole 31 c of chamber 31 is inclined to attachment surface 31i, and first portion 15 aa is bent toward burner port surface 30 b with respect to second portion 15 ab. Thus, first portion 15 aa of flame rod 15 can be disposed closer to burner port surface 30 b in combustion apparatus 200 than in the conventional combustion apparatus. Flame rod 15 can thus have higher sensing performance than the flame rod of the conventional combustion apparatus.

In combustion apparatus 200, when second portion 15 ab is configured to extend perpendicular to attachment surface 31 i to pass through flange portion 31 a, flame rod 15 interferes with heat absorption pipe 13 or burner 30. In this case, for example, the distance between heat absorption pipe 13 and burner 30 needs to be increased in order to prevent the interference of flame rod 15 with heat absorption pipe 13 or burner 30, resulting in increased sizes of the combustion apparatus and the hot water apparatus. In combustion apparatus 200, flame rod 15 can be disposed close to burner port surface 30 b without increasing the size of the apparatus.

In combustion apparatus 200, core 15 a includes first portion 15 aa which has tip end 15T and is disposed to extend along burner port surface 30 b. Tip end 15T is disposed opposite to chamber 31 with respect to burner port surface 30 b and is also disposed to overlap burner 30 in plan view.

Consequently, first portion 15 aa of flame rod 15 is disposed close to burner port surface 30 b, and the distance between burner port surface 30 b and first portion 15 aa is made approximately constant. Flame rod 15 thus has enhanced hypoxia sensing performance compared with the flame rod of the conventional combustion apparatus including no first portion 15 aa as described above.

In the combustion apparatus, core 15 a includes second portion 15 ab inserted into chamber 31, third portion 15 ac disposed between first portion 15 aa and second portion 15 ab, first bent portion 15 ad connecting first portion 15 aa and third portion 15 ac to each other, and second bent portion 15 ae connecting second portion 15 ab and third portion 15 ac to each other. As a result, compared with the case when core 15 a includes a single bent portion between first portion 15 aa and second portion 15 ab, the position of first portion 15 aa is resistant to constraints due to an angle of inclination of core 15 a to attachment surface 31 i. In other words, first portion 15 aa is disposed to extend along the burner port surface in flame rod 15, irrespective of the angle of inclination. Flame rod 15 is thus designed easily and has enhanced hypoxia sensing performance.

It is also conceivable that in order to dispose the flame rod close to the burner port surface in the conventional combustion apparatus, the flame rod may be bent at almost the right angle to the portion of the flame rod which is attached to the lateral wall of the case to dispose the tip of the flame rod close to the burner port surface. In this case, however, due to the constraints in the accuracy of assembly, the tip end of the flame rod contacts the burner port surface more easily when the flame rod is attached to the lateral wall of the case of the heat exchanger as the tip of the flame rod and the burner port surface are brought closer to each other. As a result, the burner port surface is more prone to damage.

In contrast, combustion apparatus 200 further includes burner flange 37 disposed between burner 30 and core 15 a such that at least part of burner flange 37 overlaps the outer edge portion of burner 30. In combustion apparatus 200, burner flange 37 is provided such that when flame rod 15 inserted into chamber 31 is disposed at a position different from a predetermined attachment position, burner flange 37 is disposed between burner port surface 30 b and core 15 a to prevent core 15 a disposed at the different position from contacting burner port surface 30 b. Burner flange 37 can prevent damage to burner port surface 30 b due to the contact of core 15 a bent as described above with burner port surface 30 b when flame rod 15 including core 15 a is attached to chamber 31.

In combustion apparatus 200, burner 30 has a fibrous structure. Burner flange 37 has a structure having a shape of a plate made of metal material, which is more resistant to damage upon contact with the flame rod than the structure of burner 30. Burner flange 37 as described above can prevent flame rod 15 from damaging burner 30 together with burner flange 37 when flame rod 15 contacts burner flange 37.

In combustion apparatus 200, flange portion 31 a has a through-hole into which the flame rod is inserted and a recess connected to the end on the burner side of the through-hole. The recess in the first direction extending toward the outer circumference of the burner has a width smaller than the width of the recess in the second direction orthogonal to the first direction. Such a recess can prevent the flame rod including the core bent as described above from interfering with the chamber when the flame rod is attached to the chamber.

In the combustion apparatus, the flame rod further includes an insulator covering part of the core. The combustion apparatus further includes a fixing portion that fixes the flame rod to the chamber. Fixing portion has an insertion hole into which the insulator is inserted. The insertion hole is provided to position the inserted flame rod with respect to the fixing portion. The fixing portion includes an engagement portion that engages with the chamber. The engagement portion is provided to position the fixing portion with respect to the chamber. This prevents the flame rod from being attached at a position different from a position predetermined with respect to the chamber in the combustion apparatus.

A hot water apparatus according to the present invention includes the combustion apparatus and a heat exchange unit that heats hot water by combustion gas generated through combustion of the mixed gas in the combustion apparatus. Consequently, a hot water apparatus can be provided that includes a combustion apparatus including a flame rod with high sensing performance.

Although the embodiment of the present invention has been described as above, it should be understood that the embodiment disclosed herein is illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the meaning and scope equivalent to the terms of the claims. 

What is claimed is:
 1. A combustion apparatus comprising: a burner including a burner port surface in which a plurality of burner ports are open; a chamber including an attachment surface to which the burner is attached, the chamber supplying mixed gas to the plurality of burner ports; and a flame rod attached to an outer circumferential portion of the chamber which is located on an outer circumference side of the burner in plan view, the flame rod including a core, wherein the core extends diagonally to the attachment surface to pass through the chamber, and is bent toward the burner port surface.
 2. The combustion apparatus according to claim 1, wherein the core includes a first portion having a tip end and disposed to extend along the burner port surface, and the tip end is disposed opposite to the chamber with respect to the burner port surface and is disposed to overlap the burner in plan view.
 3. The combustion apparatus according to claim 2, wherein the core includes a second portion inserted into the chamber, a third portion disposed between the first portion and the second portion, a first bent portion connecting the first portion and the third portion to each other, and a second bent portion connecting the second portion and the third portion to each other.
 4. The combustion apparatus according to claim 1, further comprising a burner flange disposed between the burner and the core such that at least part of the burner flange overlaps an outer edge portion of the burner in plan view.
 5. The combustion apparatus according to claim 4, wherein the burner flange is provided such that when the flame rod inserted into the chamber is disposed at a position different from a predetermined attachment position, the burner flange is disposed between the burner port surface and the core to prevent the core disposed at the different position from contacting the burner port surface.
 6. The combustion apparatus according to claim 4, wherein the burner has a fibrous structure, and the burner flange has a structure having a shape of a plate made of metal material, the structure being more resistant to damage upon contact with the flame rod than the fibrous structure of the burner.
 7. The combustion apparatus according to claim 1, wherein the outer circumferential portion has a through-hole into which the flame rod is inserted, and a recess connected to an end on a burner side of the through-hole, and the recess in a first direction extending toward an outer circumference of the burner has a width smaller than a width of the recess in a second direction orthogonal to the first direction.
 8. The combustion apparatus according to claim 1, wherein the flame rod further includes an insulator covering part of the core, the combustion apparatus further comprises a fixing portion that fixes the flame rod to the chamber, the fixing portion has an insertion hole into which the insulator is inserted, the insertion hole is provided to position the inserted flame rod with respect to the fixing portion, the fixing portion includes an engagement portion that engages with the chamber, and the engagement portion is provided to position the fixing portion with respect to the chamber.
 9. A hot water apparatus comprising: a combustion apparatus according to claim 1; and a heat exchange unit that heats hot water by combustion gas generated through combustion of mixed gas in the combustion apparatus.
 10. The combustion apparatus according to claim 2, further comprising a burner flange disposed between the burner and the core such that at least part of the burner flange overlaps an outer edge of the burner in plan view.
 11. The combustion apparatus according to claim 10, wherein the burner flange is provided such that when the flame rod inserted into the chamber is disposed at a position different from a predetermined attachment position, the burner flange is disposed between the burner port surface and the core to prevent the core disposed at the different position from contacting the burner port surface.
 12. The combustion apparatus according to claim 3, further comprising a burner flange disposed between the burner and the core such that at least part of the burner flange overlaps an outer edge of the burner in plan view.
 13. The combustion apparatus according to claim 12, wherein the burner flange is provided such that when the flame rod inserted into the chamber is disposed at a position different from a predetermined attachment position, the burner flange is disposed between the burner port surface and the core to prevent the core disposed at the different position from contacting the burner port surface.
 14. The combustion apparatus according to claim 2, wherein the outer circumferential portion has a through-hole into which the flame rod is inserted, and a recess connected to an end on a burner side of the through-hole, and the recess in a first direction extending toward an outer circumference of the burner has a width smaller than a width of the recess in a second direction orthogonal to the first direction.
 15. The combustion apparatus according to claim 3, wherein the outer circumferential portion has a through-hole into which the flame rod is inserted, and a recess connected to an end on a burner side of the through-hole, and the recess in a first direction extending toward an outer circumference of the burner has a width smaller than a width of the recess in a second direction orthogonal to the first direction. 